FIG. 3 shows a conventional semiconductor layer. This semiconductor layer includes an Al2O3 substrate 11 made of Al2O3, an AlN layer 12 which is formed on a surface of the Al2O3 substrate 11, and a GaN growth layer 13 which is formed on the AlN layer 12 through epitaxial growth by utilizing an MOCVD (Metal Organic Chemical Vapor Deposition) method (refer to JP 52-36117 B for example).
According to this semiconductor layer, the AlN layer 12 is formed between the Al2O3 substrate 11 and the GaN growth layer 13, whereby mismatch in lattice constants can be reduced to reduce imperfect crystalline.
However, according to the conventional semiconductor layer, the lattice constants of the AlN layer 12 and the GaN growth layer 13 cannot be perfectly made match each other, and thus it is difficult to further enhance crystal quality of the GaN growth layer 13. In addition, when the conventional semiconductor layer is applied to a light emitting element, crystalline of a luminous layer is degraded, and luminous efficiency is reduced.
Therefore, an object of the present invention is to provide a semiconductor layer in which a GaN system epitaxial layer having high crystal quality can be obtained.